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Meteoric Blast & Cooling, Some Rain Ahead

Off the top, we talk about what could've caused that loud early morning boom heard from the Sierra to Bakersfield. The likely candidate: an exploding meteor. Cooling Temps Some Drizzle, Risk of Mountain ThunderThe next two days will feature much cooler weather and possibly some very different types of weather conditions around the Bay Area. Closer to the bay and near sea level, cooler marine air will continue our cooling trend from Sunday, even reaching our inland valleys to keep temps mainly in the 50s to mid 60s near the coast and bay with some 60s to lower 70s inland. Unlike cooler marine air which is a stable layer, we?ll see daytime heating over our higher hills especially along the coastal range and into the North Bay, East Bay and South Bay hills east of San Jose that will add to daytime instability as mid-level moisture streams in from the west. An approaching trough will add a little lift over the Bay Area as well which means we could see an isolated shower or mountain thunder at times into Tuesday afternoon, mainly during the day. Expect rain to return later on Wednesday into Thursday as an area of low pressure gets pushed inland by a weather system moving in to our north. Rain should change to showers by Thursday evening (slight risk for isolated thunder then as well) with temperatures running quite cool, mainly 50s and low 60s.Perfect timing for the next warmup as high pressure rebuilds on Friday for some briefly breezy conditions and temperatures climbing back into the 60s in and 70s on Saturday. (Published Sunday, April 22, 2012)

People in Northern California and Nevada reported hearing a loud boom in the sky above the Sierra Sunday morning.

The Tuolumne County sheriff's department said they are investigating the possibility that it might have been the physical impact of an overnight meteor shower. Some people in the Tahoe area said they saw what they believed to be a meteor just prior to the sound. Others said they saw a fireball streak across the sky at the same time.

People who live in in Lake Tahoe, El Dorado County, Placer County, Tuolumne County, Amador County and Nevada County contacted our sister station in Sacramento. KCRA is reporting that they heard the sound around 8 a.m.

Tthe explosion rattled windows and shook houses from Reno to Winnemucca in Nevada, and from the Sacramento to Bakersfield.

Meteorologists in California and Nevada including our own NBC Bay Area's Rob Mayeda said there were meteor showers Saturday night that could have still been going on Sunday morning.

If the boom was a signal that an outer space rock made it way through the atmosphere, then there could be a rock or rocks now on Terra Firma. So far, no one has called authorities or television stations to report "a hit."

Depending on which expert you talk to, the meteor was the size of a man's fist up to the size of a washing machine.

Mayeda said the meteor would likely be a bolide, a meteor that explodes as it falls through the atmosphere and some pieces can survive, reaching the ground as meteorites.

Astronomers said it will take time to determine the path of the fireball and where it broke up.

"From the reports, I have no doubt it was a fireball,'' said Robert Lunsford of the Geneseo, N.Y.-based American Meteor Society told AP. "It happens all the time, but most are in daytime and are missed. This one was extraordinarily bright in the daylight.''

He added that it was pretty rare for it to cause a loud explosion. For that to happen, he explained, the meteor must have survived intact until breaking up about five miles above Earth. Most fireballs are visible at 50 miles above Earth.

"If you hear a sonic boom or loud explosion, that's a good indication that some fragments may have reached the ground,'' Lunsford said. "We'll have to get some people to work on it to pinpoint where it broke up and see if anything can be found on the ground.''

Every year the Earth passes through the orbit of a comet causing the Lyrid meteor shower. The results on a clear night is a meteor shower, which comes in the form of light streaks shooting across the night sky.

There was also a reported meteor streak in the South Bay Sunday morning around the same time. Don Hirschfeld said he was at the Capitol Flea market when he saw a brilliant green streak race across the San Jose sky in the northeast direction. Hirshfeld said it lasted just a few seconds, but caught bargain shoppers' attention. There was no boom in the San Jose event and the streak ended with burn up flashes.